Have you changed settings in your gaming PC's BIOS and it won't boot? Did you try overclocking and your system became unstable? Are you seeing error LEDs on your motherboard? You might need to clear the CMOS! Clearing the CMOS resets the BIOS settings, the software that manages your computer's core components. In this article, we'll explain what clearing the CMOS is and how to do it safely.
Clear CMOS and BIOS: what's the connection?
The BIOS ( Basic Input Output System ) is software that allows you to configure the basic settings of your computer, such as the boot order, processor frequency, memory voltage, etc. The BIOS is stored on a memory chip called CMOS ( Complementary Metal Oxide Semiconductor ), which is powered by a small battery on the motherboard.
Sometimes, the BIOS can freeze or become unstable due to improper handling, a failed overclocking attempt, a failed update, or a virus. In this case, it may be necessary to reset the BIOS to factory settings, a process known as clearing the CMOS.
Clearing the CMOS involves cutting off the power supply to the CMOS chip for a few seconds, which erases the data it contains and resets the BIOS. There are several methods for performing a CMOS clear, which we will explain in this article.
How to reset your PC's BIOS using Clear CMOS?
Method 1: Use the Clear CMOS button
Some motherboards have a dedicated button for clearing the CMOS . It's usually located on the back of the case, near the USB or audio ports. If your motherboard has one, here's how to do it:
- Turn off your computer and unplug the power supply cable or turn the power supply switch to OFF.
- Press the Clear CMOS button for 5 to 10 seconds.
- Reconnect the power supply cable or turn the power supply switch back to ON.
- Turn your computer back on and enter the BIOS to verify that the settings have been reset.
Method 2: Use the Clear CMOS jumper
If your motherboard doesn't have a Clear CMOS button, you can use a jumper to perform the same operation. A jumper is a small metal connector that allows you to connect two pins on the motherboard. You need to find the two pins dedicated to Clear CMOS, which are usually indicated by the letters CLR, CLRCMOS, CLRTC, or JBAT. You can consult your motherboard's manual to locate them. Here's how to do it:
- Turn off your computer and unplug the power supply cable or turn the power supply switch to OFF.
- Open your computer case and locate the two Clear CMOS pins on the motherboard.
- Place the jumper across the two pins for 5 to 10 seconds, then remove it. If you don't have a jumper, you can use a screwdriver or a paperclip to make contact between the two pins.
- Reconnect the power supply cable or turn the power supply switch back to ON.
- Turn your computer back on and enter the BIOS to verify that the settings have been reset.
Method 3: Remove the CMOS battery
If you can't find the Clear CMOS button or pins, you can remove the battery that powers the CMOS chip. This is a round CR2032 type battery, usually located near the processor or memory on the motherboard. Here's how:
- Turn off your computer and unplug the power supply cable or turn the power supply switch to OFF.
- Open your computer case and locate the CMOS battery on the motherboard.
- Remove the battery from its compartment, being careful not to damage the contacts. You can use a small flathead screwdriver to pry it out.
- Wait 5 to 10 seconds, then put the battery back in place.
- Reconnect the power supply cable or turn the power supply switch back to ON.
- Turn your computer back on and enter the BIOS to verify that the settings have been reset.
FAQ
What are the risks of Clear CMOS?
Clearing the CMOS is a safe operation for your computer, provided you follow these precautions:
- Turn off and unplug your computer before handling the motherboard.
- Avoid touching electronic components with fingers or metallic objects.
- Return the button, jumper or battery to their initial position after Clear CMOS.
Clearing the CMOS is a safe operation for your computer, provided you follow these precautions:
- Turn off and unplug your computer before handling the motherboard.
- Avoid touching electronic components with fingers or metallic objects.
- Return the button, jumper or battery to their initial position after Clear CMOS.
The only downside to clearing the CMOS is that you will lose all the custom settings you had made in the BIOS. It is therefore advisable to note down your settings before clearing the CMOS, or to create a profile in the BIOS to save them.
When to perform a CMOS clear?
Clear CMOS is useful in the following situations:
- Your computer does not start or freezes after changing settings in the BIOS, for example to overclock your processor or memory.
- Your computer displays error messages at startup, such as “CMOS checksum error” or “CMOS battery failure”.
- Your computer has been infected by a virus that has altered the BIOS.
- Your computer is stuck on the error message "Diagnosing your computer" and you cannot access the operating system.
- You want to reset the BIOS to factory default settings.
How do I access the BIOS?
The BIOS is accessed when you start your computer by pressing a specific key. This key varies depending on the make and model, but it is usually F1, F2, F10, F12, Delete, or Esc. You must press the key when your computer manufacturer's logo appears on the screen. If you miss the correct moment, you can restart your computer and try again.
How do I update the BIOS?
The BIOS can be updated to fix bugs, improve compatibility, or add new features. To update the BIOS, you must download the latest software version from your motherboard manufacturer's website and then install it from within the BIOS or from within Windows. Be aware that this is a delicate operation that can render your computer unusable if an error occurs or there is a power outage. Therefore, it is recommended that you carefully follow the manufacturer's instructions and do not interrupt the update process.
What is the difference between BIOS and UEFI?
The BIOS is the traditional software used to configure your computer's basic settings. UEFI (Unified Extensible Firmware Interface) is a newer software that is gradually replacing the BIOS. UEFI offers more features than the BIOS, such as a graphical interface, enhanced security, faster boot times, and support for hard drives larger than 2TB. If your computer is relatively new, it likely uses UEFI instead of the BIOS. However, the term BIOS is often used interchangeably to refer to UEFI.
Conclusion
Clearing the CMOS is an operation that resets the BIOS to its factory settings. There are several methods for clearing the CMOS, such as using a button, a jumper, or removing the CMOS battery. Clearing the CMOS is useful if you experience boot problems or computer instability after modifying BIOS settings, for example, to overclock your processor or memory. Clearing the CMOS resets the BIOS to its default settings and resolves any conflicts or errors.
We hope this article has been helpful in understanding what a CMOS clear is and how to perform it. If you have any questions or comments, please feel free to leave them below.
